In recent years, fuel cell systems, which generate electricity by supplying hydrogen (fuel gas) and air containing oxygen (oxidant gas), have been developed and are expected as power sources for fuel cell vehicles, for example. The flow rate and pressure of hydrogen supplied to the fuel cell in a fuel cell system are adjusted using, for example, regulators and injectors. Especially, when injectors are used, for example, the injection timing and injection time period of hydrogen can be finely controlled by opening and closing valve bodies with electromagnetic driving force that is applied in pulse form at an interval of a predetermined time period (interval).
For example, Patent Document 1 describes a fuel control device in which a plurality of injectors are provided in series or in parallel in hydrogen supply routes where hydrogen is supplied from a hydrogen supply unit to the fuel cell. In addition, Patent Document 1 describes to control opening and closing of the injectors such that the injectors are opened and closed at intervals of the same cycle period and the same timing.
In addition, Patent Document 2 describes respectively arranging a main supply injector and an auxiliary supply injector upstream of the ejector, and the main supply injector and the auxiliary supply injector injecting hydrogen substantially alternately with temporal phase difference.
Patent Document 1: Japan Patent Application Laid Open No. 2012-119300
Patent Document 2: Japan Patent Application Laid Open No. 2011-179333
The valve opening time period of the valve body included in the injector is controlled according to the time period electrified onto a solenoid, which is a source of generating the above-described electromagnetic driving force. It should be noted that, if we assume that ON duty is 100% during a drive interval of the injector (i.e., if the injector is continuously electrified), there is a possibility that the device suffers from fixation by being heated. Therefore, it is necessary to set a predetermined OFF time period during the interval even when driving the injectors with maximum ON duty. Meanwhile, hydrogen is consumed continuously in fuel cells. Accordingly, in the technique described in Patent Document 1, there is a possibility that hydrogen of an amount corresponding to a hydrogen requirement amount of the fuel cell cannot be supplied appropriately as a result of setting the above-described OFF time period.
In addition, when the hydrogen requirement amount is small at the starting time of the interval, the above-described ON duty of the plurality of injectors is, of course, set to a small value, and the hydrogen supply amount during the current interval is small also. Here, in the technique described in Patent Document 1, when the hydrogen requirement amount has increased rapidly before the starting time of the next interval, there may be deficiencies in stoichiometry since hydrogen cannot be supplied immediately according to such change in the hydrogen requirement amount.
In addition, in the technique described in Patent Document 2, the main supply injector and the auxiliary supply injector are arranged upstream of the ejector. Therefore, since there are pressure losses in the ejectors upon injecting hydrogen from each injector, hydrogen of sufficient flow rate may not be able to be supplied to the fuel cell.